This invention relates to a surgical trocar and more, particularly to a safety trocar in which the sharp cutting tip retracts into the cannula so as to minimize the likelihood of inadvertent injury to viscera and other internal tissue.
Trocars are sharp pointed surgical instruments used to puncture a body cavity. Trocars are generally adapted to be used together with a tubular trocar sleeve or cannula. Once the body cavity has been punctured by the trocar, the sharp trocar is removed from the cannula, thereby leaving the cannula extending into the body cavity. Endoscopic surgical procedures are then performed through the cannula with accessory instrumentation such as laparoscopes, dissectors, graspers, etc.
Commercially available safety trocars include a spring-loaded safety shield which is adapted to cover the trocar tip once the body cavity has been entered so as to provide an increased level of protection to internal structures from puncture or laceration. For example, U.S. Pat. No. 4,601,710 to Moll describes a trocar assembly which consists of two subassemblies: a trocar subassembly which includes a sharp-tipped trocar and a spring-loaded tubular safety shield positioned therearound, and a cannula subassembly.
When ready for use, the trocar and safety shield of the trocar subassembly are inserted through the cannula. The safety shield is initially in its distal-most position covering the trocar tip. Exertion of pressure against the skin with the trocar causes the shield to be pushed rearwardly against the spring to expose the piercing tip of the trocar. The tip penetrates the skin and underlying tissue with continued pressure. Once the tip has penetrated through the wall and has entered the cavity, the force against the front end of the shield ceases and the shield is automatically moved back to its distally extended position. Viscera and other internal tissue are thus protected from contact with the sharp piercing tip and potential damage therefrom.
An article entitled xe2x80x9cNeedle for the Puncture and Lavage of the Abdominal Cavityxe2x80x9d authored by F. S. Subairov discloses a safety device for puncturing the abdominal cavity which consists of a hollow tube, a stylet and a spring. The spring is soldered to the stylet and threaded into the rear of the hollow tube. The distal end of the stylet is exposed from the hollow tube by pressing the stylet toward the tube, thereby compressing the spring. Once the stylet and tube enter a body cavity, the tube is advanced under spring force to cover the distal end of the stylet. A similar device is disclosed in EP 350,291 (see FIGS. 1-4).
U.S. Pat. No. 4,535,773 to Yoon suggests several alternative safety trocar designs. In-one embodiment (see FIGS. 22-28), a spring-loaded blunt probe is provided within the trocar shaft, as with conventional Verres needles. The blunt probe is adapted to reciprocally slide through an aperture in the trocar tip such that when the trocar tip enters a body cavity, the blunt probe springs distally forward through the aperture to prevent contact between the trocar tip and body organs. In a second embodiment (see FIGS. 33-36), pressure sensors or transducers are fitted into the trocar blade surfaces and the distal end of the cannula. Sets of electrical leads run through the trocar shaft and communicate with an alarm network in the proximal portion of the device. A further modification is suggested in which the trocar shaft is initially manually extended and maintained in its extended position by a detent which protrudes through a hole in the surrounding tubular structure. The hole aligns with a solenoid socket. When the instrument is fully assembled and the trocar tip is forced through a body wall, the electrical leads running through the trocar shaft send electrical signals to the solenoid which, at the appropriate instant, forces the detent from the hole, allowing the trocar tip to withdraw into the cannula. Additional mechanisms for effecting withdrawal of cutting implements are also known. See, e.g., U.S. Pat. Nos. 4,375,815 to Burns; 3,657,812 to Lee; and 3,030,959 to Grunert.
It has now been found that an improved safety trocar may be provided which includes:
(a) a cannula assembly comprising a cannula and a cannula housing;
(b) a trocar assembly comprising a sharp trocar tip, an obturator shaft, and a trocar housing;
(c) means associated with the obturator shaft which releasably maintains the trocar tip in an extended position;
(d) means associated with the cannula assembly for releasing the releasable obturator means; and
(e) biasing means for retracting the trocar tip from the extended position to a retracted position in response to release of the releasable obturator means.
The safety trocar of the present invention is adapted to be armed by the surgeon immediately prior to use. Arming may be accomplished by advancing a button which extends through the trocar housing, by compressing the trocar housing toward the cannula housing, or by like means. Once armed, the trocar tip releasably protrudes beyond the distal end of the cannula.
As the surgeon presses the trocar, and more particularly the trocar tip, against the body wall of a patient, an incision into and through the body wall is begun. With continued pressure by the surgeon, the distal end of the cannula comes into contact with the body wall. The initial counterforce exerted by the body wall against the cannula causes a mechanism associated with the cannula to set the obturator shaft (together with the cutting tip) for immediate retraction upon entry of distal end of the the cannula into the body cavity. Thus, removal of the counterforce from the distal end of the cannula, e.g., upon entering the body cavity, results in immediate and automatic withdrawal of the trocar tip into the cannula under the force of a biasing means, e.g., a spring.
In a preferred embodiment of the trocar, a latch is associated with the obturator shaft to which the trocar tip is mounted, the latch being biased radially outward and being adapted to engage an internal shelf formed in the cannula when the trocar is armed. The cannula is reciprocally mounted to the cannula housing and biased, e.g., by a compression spring, distally relative to the cannula housing. As the trocar tip enters the body cavity and the body wall exerts force on the distal end of the cannula the cannula reciprocates proximate into the cannula housing. This cannula reciprocation repositions the cannula""s internal shelf relative to the latch such that, upon distal movement of the cannula upon entry into the body cavity, the latch is released from engagement with the internal shelf. A spring which was loaded upon arming the trocar is thus free to immediately retract the trocar tip into the cannula. In a particularly preferred trocar embodiment, abutment means are provided on the exterior of the cannula toward its distal end to facilitate reciprocation thereof through contact with the body wall.
The trocar of the invention is also designed to permit manual retraction or disarming of the cutting tip, if so desired. This is accomplished by manually reciprocating the cannula relative to the cannula housing and releasing, thereby disengaging the latch from the internal shelf. The trocar is also typically provided with an indicator which signals the surgeon as to whether the trocar is armed or disarmed. For example, the relative position of the button used to arm the trocar may be calibrated or indexed to communicate the trocar tip position or a window may be provided through which a trocar tip position indicator is visible.
The trocar of the present invention provides a safe and efficacious means for gaining access to body cavities to permit minimally-invasive diagnostic and surgical procedures to be accomplished. The trocar is equipped with a reliable mechanism for effectuating immediate, automatic retraction of the cutting tip into the cannula. Penetration force is kept to a minimum through the unique internal mechanism for releasably maintaining the trocar tip in the armed position.